Research Article Antimicrobial Susceptibility of Escherichia coli Strains Isolated from Alouatta spp. Feces to Essential Oils Valéria Maria Lara, 1 Adriano Bonfim Carregaro, 1 Deise Flores Santurio, 2 Mariangela Facco de Sá, 2 Janio Moraes Santurio, 2 and Sydney Hartz Alves 2 1 Department of Veterinary Medicine, University of S˜ ao Paulo, Avenida Duque de Caxias Norte 225, 13635-900 Pirassununga, SP, Brazil 2 Department of Microbiology and Parasitology, Federal University of Santa Maria, Avenida Roraima 1000, 97105-900 Santa Maria, RS, Brazil Correspondence should be addressed to Val´ eria Maria Lara; vallaracarregaro@gmail.com Received 28 March 2016; Accepted 9 May 2016 Academic Editor: Tierry Hennebelle Copyright © 2016 Val´ eria Maria Lara et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tis study evaluated the in vitro antibacterial activity of essential oils from Lippia graveolens (Mexican oregano), Origanum vulgaris (oregano), Tymus vulgaris (thyme), Rosmarinus ofcinalis (rosemary), Cymbopogon nardus (citronella), Cymbopogon citratus (lemongrass), and Eucalyptus citriodora (eucalyptus) against Escherichia coli ( = 22) strains isolated from Alouatta spp. feces. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for each isolate using the broth microdilution technique. Essential oils of Mexican oregano (MIC mean = 1818 g mL −1 ; MBC mean = 2618 g mL −1 ), thyme (MIC mean = 2618 g mL −1 ; MBC mean = 2909 g mL −1 ), and oregano (MIC mean = 3418 g mL −1 ; MBC mean = 4800 g mL −1 ) showed the best antibacterial activity, while essential oils of eucalyptus, rosemary, citronella, and lemongrass displayed no antibacterial activity at concentrations greater than or equal to 6400 g mL −1 . Our results confrm the antimicrobial potential of some essential oils, which deserve further research. 1. Introduction Te indiscriminate use of antibacterial agents has led to one of the largest recent global health problems which is the emergence of bacterial resistance. Several bacteria genera have developed multidrug resistance, including Escherichia coli [1]. E. coli are Gram-negative, nonsporulating facultative anaerobes, found primarily in the gastrointestinal tract of diferent species of domestic and wild animals and envi- ronments such as soil, water, and plants [2]. Tis pathogen can cause mild to severe infection, possibly leading to death from septicemia depending on the bacterial strain and its virulence, as well as host-related factors such as age and immunity [3]. In nonhuman primates, enteric infection by E. coli and the isolation of pathogenic strains from healthy animals have been documented [4]. Moreover, there are reports of the isolation of resistant and multidrug-resistant E. coli strains from wild animals [5–7]. Tis fnding is important given the increased contact between wild animals and humans, enabling cross-species transmission (CRT) of these bacteria. Additionally, the synthesis of new antimicrobials has declined in recent years. As such, new treatment options are needed to overcome bacterial resistance. Essential oils (EOs) are volatile and complex natural products derived from the secondary metabolism of plants and can be found in diferent plant parts, including the leaves and stalk. EOs probably consist of 20 to 60 diferent compounds, in which at least two or three are in higher concentrations, depending on the EOs [8]. Tese compounds exhibit signifcant therapeutic and pharmacological potential as well as antimicrobial properties, already established for Gram-positive bacteria and Gram-negative bacteria found in diferent animals species, including humans [7–16]. Te main compounds with possible antimicrobial activity are Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2016, Article ID 1643762, 4 pages http://dx.doi.org/10.1155/2016/1643762